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Nutrition (Ch. 25)

Nutrition, Metabolism & Body Temperature Regulation

what is ATP the chemical energy form used by cells to drive their many activities
the energy value of foods is measured in units called kilocalories
one kilocalorie is the amount of heat energy needed to raise the temperature of 1 kilogram of water 1C & is the unit conscientiously counted by dieters
major nutrients are carbohydrates, lipids & proteins
what is a nutrient a substance in food that is used by the body to promote normal growth, maintenance & repair
essential nutrients cannot be made by such interconversions & must be provided by the diet
what is cellulose a polysaccharide plentiful in most vegetables, not digested by humans but provides roughage or fiber
glucose is a monosaccharide carbohydrate molecule; major body fuel & is readily used to make ATP
carbohydrate digestion yields gructose & galactose (converted to glucose by the liver before they enter the general circulation)
when glucose is present in excess of what the body needs for ATP synthesis, it is converted to glycogen or fat & stored for later use
what is the current recommendation of charbohydrates daily 125 to 175 grams
what is the term used to describe highly refined carbohydrates such as candy & soft drinks empty calories
what are the major sources of unsaturated fats seeds, nuts & most vegetable oils
major sources of cholesterol are egg yolk, meats (organ meats like liver) & milk products
the liver cannot synthesize linoleic acid, a fatty acid component of lecithin
an example of an essential fatty acid is linoleic acid
what do fatty deposits in adipose tissue provide? (1) protective cushion around body organs such as kidneys & eyeballs (2) insulating layer beneath the skin (3) easy-to-store concentrated source of energy fuel
prostaglandins regulatory molecules; plays a role in smooth muscle contraction, control of blood pressure & inflammation
how are prostaglandins formed from linoleic acid via arachidonic acid
why is cholesterol important it is used as a stabilizing component of plasma membranes & is the precursor from which bile salts, steroid hormones & other essential functional molecules are formed
daily cholestrol intake should be no more than 200 mg (the amount of one egg yolk)
name two drawbacks to most fat substitutes (1) don't stand up to the inense heat needed to fry foods (2) dont taste nearly as good as the "real thing"; the ones that are not absorbed tend to cause flatus (gas) & may interfere w. absorptionof fat-soluble drugs & vitamins
what are complete proteins they meet all the body's amino acid requirements for tissue maintenace & growth
what is the importance of proteins in the body? keratin of skin, collagen & elastin of connective tissues & muscle proteins
what is the all or none rule all a.a. needed to bake a particular protein must be present in a cell @ the same time; if one is missing protein will not be made
why does this happen b.c. essential amino acids cannot be stored, therefore those not used immediately to build proteins are oxidized for energy or converted to carbohydrates or fats
what happens if the diet does not supply sufficient carbohydrate or fat calories for ATP production dietary & tissue proteins are used for energy
what is the percentage of nitrogen content of protein 16%
when is the body in nitrogen balance when the amount of nitrogen ingested in proteins equals the amount excreted in urine & feces
explain when the body is in positive nitrogen balance when protein synthesis exceeds protein breakdown & loss (normal in growing children & pregnant women); also occurs when tissues are being rebuilt or repaired following illness or injury
what does a positive nitrogen balance always indicate that the amount of protein being incorporated into tissue is greater than the amount being brokendown & used for energy
a negative nitrogen balance is protein breakdown exceeds the use of protein for building structural or functional molecules
when would negative nitrogen balance occur during physcal & emotional stress (infection, injury, burns, depression or anxiety) during starvation
what are anabolic hormones they accelerate protein synthesis & growth
give an example of how an anabolic hormone works pituitary growth hormone stimulates tissue growth during childhood & conserves protein in adults
give another example the adrenal glucocorticoids released during stress, enhance protein breakdown & conversion of amino acids to glucose
most vitamins function as ____ coenzymes; that is they act w. an enzyme to accomplish a particular chemical task
why are vitamins crucial they help the body to use those nutrients that do; w.o. them all carbs, proteins & fats would be useless
where is vitamin D made in the skin
what vitamins are syntehsized by intestinal bacteria B & K
how are vitamins classifyied as fat soluble or water soluble
what are examples of water souble vitamins B-complex vitamins & vitamin C
what are water souble vitamins they are absorbed along w. water from the gastrointestinal tract (w. exception to B12 which must bind to gastic intrinsic factor to be absorbed)
water-souble vitamins can easily be stored & if theyre not used can be excreted in urine
what are the fat-soluble vitamins A, D, E, K
what do fat-soluble vitamins they bind to ingested lipids & are absorbed along w. their digestion products
what can interfer w. fat-soluble vitamins anything that interferes w. fat absorption
what are antioxidants they disarm tissue-damaging free radicals & have anticancer effects
what are examples of antioxidants? vitamins A, C, & E
list the 7 minerals needed calcium, phosphorus, potassium, sulfur, sodium, chloride & magnesium
what is the purpose of calcium, phosphorus & magnesium salts they harden the teeth & strengthen the skeleton
most minerals are inonized in body fluids or bound to organic compounds to form molecules such as phospholipids, hormones, enzymes & other functional proteins
give an example of how this works iron is essential to the oxygen-binding heme of hemoglobin; sodium & chloride ions are major electrolytes n blood that help maintain (1) normal osmolarity & water balance of body fluids (2) responsiveness of neurons & muscle cells to stimuli
anabolism synthetic; includes reactions in which larger molecules or structures are built from smaller ones; ex. bonding of amino acids to make proteins & of proteins & lipids to form cell membranes
catabolism process that break down complex structures to simpler ones; ex. hydrolysis of foods in the digestive tract
cellular respiration primary function is to generate ATP, which traps some of the chemical energy of the original food molecules in its own high-energy bons; group of reactions which food fuels (particularly glucose) are broken down within cells & some of the energy released
phosphorylated when enzymes shift their high-energy phosphate groups to other molecules
what does phosphorylation do it energizes, or primes, the molecule to change in a way that increases its activity, produces motion or does work; ex. many regulatory enzymes that catalyze key steps inmetabolic pathways are activated by phosphorylation
oxidation reactions the energy-yielding (ATP-yeilding) reactions within cells;
when does oxidation occurs via the gain of oxygen or the loss of hydrogen
when on substance loses electrons it is oxidized
when one substance gains electrons it is reduced
redox reactions means that "oxidized" substances lose energy & "reduced" substances gain energy as energy-rich electrons are transferred from the first to the second
dehydrogenase when enzymes that catalyze oxidation-reduction reactions by removing hydrogen
oxidases those catalyzing the transfer of oxygen
coenzymes act as reversible hydrogen (or electron) acceptors, becoming reduced each time a substrate is oxidized
NAD+ nicotinamide adenine dinucleotide; based on niacin
FAD flavin adenine dinucleotide; derived from riboflavin
substrate-level phosphorylation occurs when high-energy phosphate groups are transferred directly from phosphorylated substrates (metabolic intermediates) to ATP
the enzymes catalyzing substrat-level phosphorylation are located in both the cytoplasm & in the watery environment inside the mitochondria (mitochondrial matrix)
oxidative phosphorylation releases most of the energy that is eventually captured in ATP bonds during cellular respiration
how is the oxidative phosphorylation process carried out? by electron transport proteins forming part of the cristae membranes in the mitochondria
chemiosmotic process couples the movement of substannces across membranes to chemical reations; some of the energy released during the oxidation of food fuels is used to pump hydrogen ios or protos across the inner mitochondrial membrane into the intermembrane space; creating
ATP synthase a membrane channel protei that allows protons to flow back across the membrane
the catabolic & anabolic pathways for carbohydrates all begin with glucose-6-phosphate
glycolysis "sugar spliting"; 10 chemical steps;
glycolysis results in two pyruvic acid molecules; yielding a net gain of 2 ATP per glucose molecule; 2 moecules of reduced NAD+
where does glycolysis occur in the cytosol of cells, where its steps are catalyzed by specific soluble enzymes
what type of process is glycolysis an anaerobic process; meaning it does not use oxygen & occurs whether or not oxygen is present
In step 1 of glycolysis ATP is consumed-an energy investment that will be repaid with dividends later in glycolysis
are the steps in glycolysis reversible all except the 1st one
list the 3 main stages in glycolysis listed in the book 1. sugar activation 2. sugar cleavage 3. oxidation & ATP formation
what's going on during the 2nd stage fructose-1, 6-diphosphate is split into 3-carbon fragemnts that exist (reversibly) as one of 2 isomers; glyceraldehyde 3-phosphate or dihydroxyacetone phosphate
lactic acid is the production yeild of two adition hydrogen atoms to pyruvic acid
when glucose is completely oxidized how many ATP/glucose molecues are harvested 36
where does the Krebs cycle occur? in aqueous mitochonrial matrix & is fueled largely by pyruvic acid produced during glycolysis & by fatty acids resultig from fat breakdown
what is the first order of bussiness during the Krebs cycle after pyruvic acid enters the mjitochondria to convert it to acetyl CoA
1) decarboxylation when one of the pyruvic acid's carbons is removed & released as carbon dioxide gas (a waste product of metabolism) CO2 diffuses out of the cells into the blood to be expelled by the lungs
2)oxidation the removal of hydrogen atoms; the removed hydrogens are picked up by NAD+
how is acetyl coenzyme A the final product by combining the resulting acetic acid w. coenzyme A
what is coenzyme Al a sulfur-containing coenzyme derived from pantothenic acid , a B-vitamin
keto acids when atoms of citic acid are rearranged to produce different intermediate molecules
what are the products of the Krebs Cycle/Citric acid cycle 2 molecules of carbon dioxide & 4 molecules of reduced coenzymes (3NADH + H+ & 1 FADH2)
electon transport chain oversees the final catabolic reations that occur on the inner mitochondrial membranes
whats going on during the ETC the hydrogens removed during the oxidation of food fuels are finally combined w. molecular oxygen, & the eergy released during those reactions is harnessed to attach inorganic phosphate groups (Pi) to ADP
cofactors proteins bound to metal atoms
where do flavins derive from the vitamin riboflavin
list the sequence energy flows during cellular respiration glucose-NADH + H+ - electron transport chai - proton motive force - ATP
the 8 NADH + H+ & the 2 FADH2 produced during the KRebs cycle are "worth" 24 & 4 ATPs
the 2 NADH + H+ generated during glycolysis yields how many ATP molecules 4 (or 6) ATP molecules
complete oxidation of 1 glucose molecule to carbon dioxide & water yields 38 or 36 molecules of ATP
glycogenesis occurs when (glycolysis is "turned off" by high ATP levels, glucose molecules are combined in long chains to form glycogen);
how does glycogenesis begin when glucose entering cells is phosphorylated to glucose-6-phosphate & the coverted innto its isomer, glucose-1-phosphate
glycogenolysis occurs when blood levels of glucose drop, glycoge lysis or splitting occurs
beta oxidation the initial phase of fatty acid oxidation, ocurs in the mitochondria
glyceraldehyde is equal to half a glucose molecule & ATP energy harvest from its complete oxidation is approx. 1/2 that of glucose (18 ATP/glycerol)
lipogenesis triglyceride sythesis; occurs when cellular ATP & glucose levels are high
lypolysis (fat-splitting); the breakdown of stored fats into glycerol & fatty acids, essentially lipogenesis in reverse
Before amino acids can be oxidized for energy they must be deaminated; their amine group (NH2) must be removed; resulting molecule then converted to pyruvic acid or one of the keto acid inntermediates in the Krebs cycle
what state does the body exist in dynnamic catabolic-anabolic state
what are the differences between the carbohydrate/fat pool & the amino acid pool? 1) fats & carbohydrates are oxidized directly to produce cellular energy, whereas a.a. can be used to supply energy only after being converted to a carbohydrate intermediate (keto acid) 2) excess carb. & fat can be stored as such, whereas excess aa are no
absorptive state fed state; the time during & shortly after eating, when nutrients are flushing into the bloodstream fm the gastorintestinal tract
postabsorptive (fasting) state period when the GI tract is empty & energy sources are supplied by the breakdown of body reabsorbes
elevated amino acid levels in the blood stimulate insulin release
what type of hormone is insulin a hypoglycemic hormone
glucose sparinng the increased use of noncarbohydrate fuel molecules (especially triacylglycerols) to conserve glucose
glucagon insulin antagonist
what type of hormone is glucagon hyperglycemic hormone; promotes a rise in blood glucose; targets the liver & adipose tissue
increasing blood sugar levels trigger insulin release
which "pushes"___ into the cells glucose
blood sugar levels decline
when blood sugar levels are low the secrtion of ___ occurs glucagon
which ___ pulls glucose from the cells into the blood
growth hormonne secretion is enhanced by prolonnged fasting or rapid declines in plasma glucose levles, & it exerts important ant-insulin effects
list the functions of the liver 1) packages fatty acids into forms that ca be stored or transported 2) synthesizes plasma proteins 3) forms nonessential aa & convertes ammonia resulting from their deamination to urea a less toxic excretory product 4)stores glucose as glycogen & regulate
cholesterol dietary lipid; serves as the structural basis of bile salts, steroid hormones & vitamin D & a mj component to plasma membrane
chylomicrons transport absorbed lipids from the gastrointestinal tract, considered as a separate class & have the lowest density of all
what is the role of LDLs to transport cholesterol tot he peripheral tissues, makinng it available tot he tissue cells for membrane or hormone synthesis & for storage for later use; also regulate cholesterol synthesis in the tissue cells
what is the function of HDLs to transport excess cholesterol from peripheral tissues (which do not have the ability to degrade or excrete HDL) to the liver, where it is broken down & becomes part of bile
HDL is considered good
LDL is considered BAD TO THE BONE!!!
what is wrong with LDL it promotes plaque formation that thickens & stiffens the blood vessel walls
saturated fatty acids stimulate ____ of cholesterola & _____ from the body liver synthesis; inhibit its excretion
what is energy intake total energy output (heat + work + energy storage)
EI is considered equal tot eh energy liberated during food oxiation; undigested foods are not part of the equation bc they contribute to no energy
Energy output includes the energy (1) immediately lost as heat (about 60% of the total); used to do work ; stored in the form of fat or glycogen
orexins a pair of peptides that are powerful appetite enhances
neuropeptide Y causes us to crave carbohydrates
galanin produces a yen for fats
GLP-1 & serotonin (glucagon-like peptide); make us feel full & satisfied
when we eat plasma glucose levels ___ & cellular metabolism of glucose __ increases; increases
elevated plasma levels of amino acids ___ eating; wheras low amino acid levels in blood ___ it. depress eating; stimulate it
insulin released during food absorption has what effect on hunger depresses hunger
glucagon levels rise during what type of behavior fasting; stimulate hunger
when is epinephrine release & what does it trigger (released during fasting); triggers hunger
what is cholecystokinin & what effect does it have on hunger? a hormone released in the intestines; it is secreted during food digestion which depresses hunger
increased body temperature may have what effect on hunger it may inhibit it
leptin the overall satiety signal; secreted over a period of hours exclusively by fat tissue in response to an increase in fatty mass in the body; regulated by glucocorticoids & insulin
what does leptin bind to receptors in the choroid plexuses of the ventricles, where it gains entry to the brain
leptin acts on the hypothalamus
what does it regulate the amount of body fat via controls of appetite & energy output
what is leptins main target of action the ventromedial hypothalamus, where it suppresses the secretion of nneuropeptide Y (NPY); the most potent appetite stimulant known
therefore with all that said & done leptin pretty much decreases food intake & cranks up activity & heat production
metabolic rate the body's rate of eergy output (usually per hour)
calorimeter direct method
respirometer indirect method; measure oxygen consumption, which is directly proportional to heat production
BMR(basal metabolic rate) the measurement obtained; reflects the energy the body nees to perform only its most essential activities
the taller or thinner person will have a ___ BMR than a shorter fatter person higher
thyroxine produced by thyroid gland; important in determing BMR; metabolic hormone
TMR (total metabolic rate) a total rate of kilocalorie connsumption to fuel all ongoing-activities--involuntary & voluntary
dietary/food-induced thermogenesis when food ingestion induces a rapid increase in TMR; is greates when proteins are eatten
radiation loss of heat in the form of infrared waves (thermal energy); close to 1/2 of body heat loss occurs by radiation
conduction transfer of heat between objects that are in direct contact w. each other; ex. when we step into a hot tup, some of the heat of the water is transferred to our skin; conduction requires molecule-to-molecule contact of objectes; thermal energy must move th
convection substantially enhances heat exchange from teh body surface tot eh air bc the cooler air absorbs heat by conduction more rapidly than the already-warmed air
the hypothalamus receives afferent input from peripheral thermoreceptors & central thermoreceptors
the hypothalmus respons the heat promoting or heat loss activites via autonomic effector pathways
vasoconstriction of cuanneous blood vessels blood is restricted to deep body areas & largely bypasses the skin; heat loss from the shell is dramatically reduced & shell temp drops toard that of the external environment
increase in metabolic rate (blank)
cold stimulates the relae of norepinephrine; elevates the metabolic rate; which enhances heat production (known as chemical; nonshivering thermogenesis)
shivering increases body temp bc muscle activity produces large amounts of heat
enhanced thyroxine release occurs when envir temp decreases gradually; hypothalamus releases thyrotropin-releasing hormonne; increases metabolic rate body heat production increases allowing us to maintain a constannt body tempin cold envir condtions
vasodilation of cutaneous blood vessels allows vessels to dialate; skin swell w warm blood, heat is lost from the shell by radiation, conduction & convection
enhanced sweatinng occurs when body is overheated & heat cannot be lost by other means; evaporation
fever is controlled hyperthermia; results from infection; occurs when wbc & macrophages release PYROGENS (fire starters)
Created by: Brina